The present invention generally relates to wind speed measurement and direction indicating apparatus. More particularly, the present invention relates to such apparatus particularly adapted for use by pilots of planes, helicopters, gliders, and hang gliders to provide a visual indication of wind conditions when taking off or landing such a vehicle.
Traditionally, recreational pilots of hang gliders or other flying apparatus determine wind direction and approximate speed by visually observing a wind sock. Conventional wind socks include an opening through which wind blows and expands the sock by an amount proportional to the size and material composition of the wind sock. However, due to their flaccid nature, these wind socks are not responsive to or accurate indicators of changes in the wind's characteristics. Such changes constantly occur near the edge of a cliff where a hang glider may be taking off, or on top of a building where a helicopter may be taking off or landing, or along a runway where wake turbulence from preceding air craft can occur, or where the presence of towers and other objects produce turbulent shearing winds. Thus, while a wind sock may convey to a pilot very general information regarding the wind, they do not provide an accurate indicator in areas where turbulence may create constantly changing wind characteristics.
Although almost exclusively used by hang gliding enthusiasts, wind socks are particularly inaccurate, and potentially dangerous. Hang gliding requires a pilot to launch from the top of a ridge or from the ledge of a cliff, the wind characteristics near the cliff need to be known for absolute efficiency and success in taking off. "Ridge lift" is the phrase used to describe certain wind characteristics that can occur near a hill or cliff. As the air mass passes over the hill, the air in contact with the hill's vertical surface is compressed and forced up and over the contour of the land. This air mass is what pilots launch into, and of course it is necessary to launch when the air mass is lifting and not sinking.
A wind sock (or simple cloth streamer) is anchored at one end with their remaining portions hanging free from the anchored end. The free end of the streamer/sock has the compressed air coming up the hill or off of the ledge passing both thereunder and thereover. If the compressed air passing under the streamer/sock is stronger than the air passing over the streamer/sock, then it will indicate the wind direction only, not the presence of lifting or sinking air. Due to the fact that streamers/socks are not statically balanced, the only indication given is wind direction when in fact the air mass may actually be sinking or lifting. These characteristics are impossible to assess from wind direction only. However, due to gravity's effect on the free end, the lift must be substantially greater than what is required to takeoff in order for it to be indicated by the streamer/sock. Hence, since the hang gliders need the optimum lift present in the air after they've launched, the streamer/sock may have indicated the optimum direction when it was over land, not out in front of the land. Therefore, the streamer/sock may be indicating optimum direction, but due to the necessary strength of the wind for the streamer/sock to so indicate, and the rapidly changing characteristics of the wind in the presence of a cliff, the air mass being launched into may actually be sinking. Thus, when a streamer/sock indicates adequate takeoff conditions, in reality the hang glider may rapidly sink to the ground.
In addition to knowing wind direction characteristics, it is also important to know wind speed. When launching a hang glider, the speed of the wind is generally estimated based on how full the wind sock gets. However, due to the previously discussed inaccuracies with wind socks, the actual wind speed is probably far from the speed estimated. Therefore, anemometers are utilized where wind speed must be accurately determined. Thus, wind speed and wind direction need different instrumentation to provide an accurate qualitative assessment thereof. U.S. Pat. No. 4,152,933 to Woodhouse on May 8, 1979 describes a system incorporating such features.
Accordingly, it is therefore a principal object of the present invention to provide a new and improved device which accurately provides a qualitative assessment of both wind direction characteristics and wind speed.
It is a further object of the present invention to provide wind speed and direction indicating device capable of providing pilot of a hang glider with means for assessing optimum takeoff conditions.
It is another object of the present invention to provide wind speed and direction indicating device which provides anyone with accurate information regarding all dimensions of the wind directions.
It is still a further object of the present invention provide a wind speed and direction indicating device which can easily transportable.
It is yet an additional object of the present invention provide a wind speed and direction indicating device which durable and resistant to UV degradation.
It is another object of the present invention to provide wind speed and direction indicating device which provides safer equipment for all pilots.
Other objects and advantages of the present invention will in part be obvious and in part appear hereinafter.